Electroplating apparatus



June 13, 1961 R. E. BELKE 2,988,497

ELECTROPLATING APPARATUS Filed May 25, 1960 s Sheets-Sheet 1 INVEN TOR. 40 A: MA Z BY [/55 AV June 13, 1961 R. E. BELKE ELECTROPLATING APPARATUS 3 Sheets-Sheet 2 Filed May 23, 1960 INVENTOR. 194 E. 65265 June 13, 1961 R. E. BELKE ELECTROPLATING APPARATUS 5 Sheets-Sheet 3 Filed May 25, 1960 2,988,497 ELECTROPLATIN G APPARATUS Ralph E. Belke, Lincolnwood, lll., assignor to Belke Manufacturing Co., Chicago, 11]., a corporation of Illinois Filed May 23, 1960, Ser. No. 31,127 3 Claims. (Cl. 204-213) The present invention relates to electroplating apparatus and methods of electroplating, and is particularly concerned with the provision of improved electroplating barrels and the methods of electroplating articles which are carried out by the use of such improved barrels.

In the electroplating of small articles according to the prior art the articles are placed ina rotating barrel which has a plurality of flat sides adapted to cause the articles to tumble over and over as the barrel rotates. The barrel is generally completely immersed in the electrolyte; and the barrel is provided with one or more electric connections in the form of a contact carried by a flexible, insulated conductor which extends into the barrel from one or both ends through an axially located bore located in one or more trunnions on the barrel.

The wall of the barrel according to the prior art is provided with a multiplicity of small apertures; and the electrolyte in a tank, in which the barrel is immersed, has access to the interior of the barrel through these apertures, which also pass electric current, passing through the electrolyte in the apertures to the articles to be electroplated.

The metal which electroplates the articles is carried from an electrode in the electroplating solution by the electrolyte, which penetrates to the interior of the barrel.

The size of the apertures in the wall of the barrel may be quite small, such as one-sixteenth of an inch in diameter, to prevent the articles, which may also be quite small, from getting into the apertures; and when the size of the apertures is in this range, there is a tendency for the electrolyte in the barrel to become starved of electroplating metal because there is a greater resistance to the passage of electrolyte through the smaller apertures; and the electroplating metal in the barrel becomes used up.

One of the objects of the invention is the provision of improved electroplating barrels which are so constructed that the rotation of the barrel automatically causes the electrolyte to be periodically driven out of the barrel down to a predetermined level which still covers the articles being electroplated, and thereafter automatically causes the entrance of a new supply of plating metal solution to be introduced into the barrel by atmospheric pressure.

Another object of the invention is the provision of an improved method of handling articles to be electroplated in such manner that the electrolyte in the barrel does not become starved of plating metal, but in which the elec/ trolyte is periodically changed by being partially exhausted from the barrel and providing a new supply of electrolyte from the outside.

In the methods of the prior art employing electroplating barrels it has been customary for such plating barrels to be wholly immersed in the electrolyte for the reason that electrolysis usually involves the generation of hydrogen gas, which is explosive when mixed with air or oxygen; and an explosion might be caused in the barrels of the prior art if hydrogen gas was permitted to collect in the barrel, where an electric spark might occur, causing an explosion.

According to the present method of electroplating, the barrel is eccentrically mounted at both its ends to be depressed into the electrolyte when it rotates toward its lowermost position; and it is raised in the electrolyte when it is moved to its uppermost position. The level of the hired rates Patent "ice electrolyte is preferably such that even in the uppermost position the charge of articles to be electroplated is still completely immersed in electrolyte so that the plating goes on continuously; but the raising and lowering of the electrolyte in the barrel causes the liquid'to be positively discharged from the barrel due to the change in level of electrolyte inside the barrel and outside the barrel when the barrel rises.

In the same manner the raising of the barrel draws in fresh air at the top when it is rising to its uppermost position; and when the barrel is depressed to its lowermost position, the difference in level of liquid inside and outside the barrel causes the electrolyte to run into the barrel through the apertures in the wall of the barrel; and the gas in the barrel is forced out through the uppermost apertures by the rising liquid.

The proportions of the parts are preferably such that when the barrel is depressed in the liquid, substantially all of the gas in the barrel is expelled.

The hydrogen, which is the result of electrolysis, tends to rise to the top of the gas in the barrel because hydrogen is lightest in weight; and thus the present method accomplishes the periodic expulsion of the gaseous products of electrolysis from the barrel in a thin and diluted nonexplosive state.

One of the further objects of the invention is the provision of an improved barrel and method of electroplating by means of which the electrolyte inside the barrel is periodically replenished, carrying new metal in the solution for electroplating, and by means of which the gaseous products of electroplating are periodically discharged from the barrel, preventing any large accumulation of hydrogen gas.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the three sheets of drawings accompanying this specification,

FIG. 1 is a view in perspective of a complete portable electroplating barrel assembly embodying the invention;

FIG. 2 is a side elevational view of the barrel with the barrel in the uppermost position which it reaches in the course of its rotation;

FIG. 3 is an end elevational view of the barrel taken on the plane of the line 44 of FIG. 2;

FIG. 4 is a fragmentary view in perspective of the end construction of the barrel;

FIG. 5 is a diagrammatic end view of a barrel, showing its relation to the liquid level in the tank when the barrel has reached its uppermost position;

FIG. 6 is a similar view, showing the barrel when it has reached its lowermost position;

FIG. 7 is a View in perspective of a modification showing another form of barrel which may be used for small batches;

FIG. 8 is another view in perspective showing another modification of the barrel which may be employed for two small batches;

FIG. 9 is a diagrammatic end elevational view showing the installation of the portable barrel assembly in a tank.

Referring to FIGS. 1-4, 10 indicates in its entirety a portable electroplating barrel assembly embodying the invention. This assembly preferably includes a pair of frame plates 11 and 11a, comprising rectangular sheets of insulating material, such as Lucite. The two plates are secured in parallel position to form a framework by a plurality of horizontal tie rods 12, 13, 14; and the tie rods may be of any suitable cross section, provided the ends are formed with threaded portions 15 adapted to receive washers and nuts 16 on the inside and similar washers and nuts on the outside, clamping the frame plates 11 and 11a on both sides, holding them in rigid parallel position.

The other tie rods 13 and 14 may be rectangular in cross section and provided with similar threaded ends, having similar washers and nuts clamping the frame plates 11 and 11a through which they pass.

Thus the frame of the portable unit has its frame plates 11 and 11a held in rigid spaced relation parallel to each other. Each frame plate 11 and 11a may also support a bus bar 18, 19 of suitable metal, such as copper, bolted to the end plate by through bolts and nuts 20 in each case; and the bus bars may be coated over all with plastic insulation, except at one end, where a V shaped slot 21 is provided for connection to a copper cathode rod 74 carried by the tank upon which the bus bars 18 rest.

The other end of each bus bar 18, 19 projects from the frame plates 11 and 11a to rest on top of the anode rod 71. Each bus bar 18, 19 is electrically connected by a suitable through bolt and nut 22 to an insulated flexible electric conductor 23, which extends through the trunnions 24 into the interior of the barrel 25, where each conductor is provided with a rounded contact 26 depending into engagement with the articles to be electroplated in the barrel.

The anode rods 70, 71 support anodes 73 hanging into the electrolyte.

Each barrel preferably comprises a circular end plate 27, 28 at each end and a barrel wall 29, extending at right angles to the end plates, and having its ends 30, 31 mounted in a complementary groove in each end plate and cemented therein, all of the assembly being made of a suitable plastic, such as Lucite, Melamine, Tempron, or other chemically inert materials.

The barrel wall 29 preferably comprises a rectangular sheet of the plastic material bent to form a regular polygon in end elevation with integral bends at 32, 33, 34, '35 and one open side 36, forming a door opening bounded by the end plates and the edges 37, 38 of the barrel wall.

Various shapes of barrels may be employed, such as round barrels with internal ribs, triangular barrels, rectangular barrels, hexagonal barrels, octagonal barrels, pentagonal barrels, etc., the purpose being to provide the barrel with a plurality of fiat sides 39, causing the articles to be electroplated to tumble over and over as the barrel rotates, to cause the electrolyte to gain access to all sides of the articles by tumbling them over and over in the solution.

To retain the articles in the barrel, it is provided with a cover 40, comprising a rectangular opening for the door opening 36, comprising a rectangular sheet of Lucite, which is bent at 41, 42 to engage over the edges 37, 38 of the barrel and to overlap the adjacent side walls 39, 39 of the barrel to effect a secure closure.

Any suitable fiat cover may be used; but, if desired, the cover 40 may be rounded at 41, 42 to form a recess between the body portion 43 of the cover and the overlapping flanges 44.

The end plates are preferably cut away along the lines 45, 46 on the inside to form a shallow groove 47, which extends radially inward to communicate with the groove in which the wall is embedded, thus permitting the cover 40 to overlap the barrel over its full length.

Each end plate is preferably provided with a rectangular slot 48 for receiving a turnbuckle 49 pivotally mounted on the cover by a through screw bolt 50; and the turnbuckle may be tapered to a thin end fitting in the slot 48 and securing the cover on the barrel at each end. The slot 48 is wide enough to receive the turnbuckle 49 and long enough to permit its rotation.

Each end plate 27, 28 is provided with a cylindrical trunnion 24 extending through an aperture 51 in each frame plate 11, 11a; and the trunnions 24 comprise cylindrical members of Lucite with a cylindrical head 52 cemented in each end plate 27, 28 and provided with the through bore 53 for passing the dangler, comprising the flexible cables 28, about which the trunnion rotates.

The barrel wall is preferably located eccentrically I with respect to the axis of the trunnions 24, which involves locating the groove for the ends '30 and 31 of the barrel toward one side of the circular end plates 27, 28.

The proportions and sizes of end plates and barrel are preferably such that the barrel is large enough in diameter so that the trunnions 24 and apertures 53 in the trunnions are located above the level of the charge of articles in the barrel; and the level of the electrolyte in the tank at 54 (FIGS. 5 and 6) is always above the articles to be electroplated, so that electroplating may proceed continuously.

One of the end plates 27 is preferably provided with a Lucite gear 55 larger in diameter than the end plate; and the gear is secured to the end plate 27 to rotate the end plate and the barrel.

The gear is secured to the end plate 27 by fiat head screws, the heads of which are countersunk and covered with Lucite so that they do not plate. Thus the gear 55 is removable for replacement. The gear 55 is adapted to mesh with a driven gear 55a rotatably mounted on a suitable shaft in a gear reduction box 56 having a control lever 57 and having its shaft driven by an electric motor 58.

The gear reduction box and motor are mounted by suitable bolts on a Lucite plate 59, which is bolted to the tie rods 13, 14. The speed of the motor and gear reduction is preferably such that the barrel rotates relatively slowly, such as about four revolutions per minute.

This rate of rotation may be varied, depending on the size of the apertures in the barrel wall and the time that it takes for the solution to pass through these apertures and maintain its level inside the barrel in accordance with the level 53 outside the barrel.

The barrel wall 29 is provided with a multiplicity of relatively small through apertures 60 regularly spaced from each other and permitting the solution to run into and out of the barrel as the barrel rotates.

The electrolyte in the apertures 60 also passes the current to the dangler contacts 26 and to the articles inside the barrel; and the size of these apertures may be varied, such as, for example, one-sixteenth of an inch in diameter, or they may be larger or smaller, provided they are not so small as to impede the passage of the solution.

Since that portion of the end plates 27 and 28 which extends outward from the barrel 25 and does not close the end of the barrel beyond the cover, the circular end plates may have that portion cut off; and only those portions of the end plates which cooperate with the barrel wall and the cover are actually essential.

Referring to FIG. 7, this is a modification in which the barrel wall 61 is hexagonal, but tapered from the left end to the right with its interior covering the trunnions 24 at each end; but the barrel is of similar construction to provide a chamber for a smaller batch of articles to be electroplated.

The cover 62 is correspondingly tapered and shaped to close the open side.

Referring to FIG. 8, this is a modification in which the two end walls 63, 64 support a pair of tapered barrel walls 65, 66 mounted in grooves in the center wall 67, which forms a partition, separating the barrel assembly into two smaller chambers for smaller batches.

The end walls 63 and 64 include the same trunnions 24 for passing a dangler into each of these chambers; and one of the end walls may be eliminated, while the Lucite gear 63 has its body grooved to receive the barrel wall, performing both the functions of a gear and an end wall.

One of the mostimportant features of the invention is a type of construction which is adapted to effecta change of the metal content of the solution inside the barrel when the holes in the barrel wall are so small that the solution does not flow through the holes in sufiicient quantity, when the barrel is rotated on its axis according to the prior art.

The cover comprises a pair of tapered members 68, each provided with a turnbuckle; and the barrels which are shown in FIGS. 7 and 8 are also eccentrically mounted to perform the same functions as those shown in FIGS. l6.

The operation of electroplating barrels of the eccentric type is illustrated in FIGS. 5 and 6, in which the level 53 of electrolyte is above the trunnions and above the articles in the barrel at all times; but the barrel rotates through the positions of FIGS. 5 and 6 to cause the solution to be expelled from the barrel as the barrel rises from the position of FIG. 6 to that of FIG. 5; and new electrolyte is taken into the barrel as it rotates from the position of FIG. 5 down to that of FIG. 6.

At the same time a fresh supply of air is taken into the barrel as it rises to the position of FIG. 5; and the hydrogen, which rises to the top of the barrel, is expelled with the air as the barrel moves down to the position of FIG. 6.

Thus the barrel is so arranged that the solution never becomes starved of electroplating metal. The hydrogen, which results from electroplating inside the barrel, is discharged from the barrel as the barrel again falls with solution to the position of FIG. 6; and the dangerous accumulation of hydrogen is avoided.

These operations are accomplished according to the present invention without the necessity of providing a separate motor and pump for the electrolyte; and thus the present eccentric electroplating barrels may be manufactured more economically than those which require an electrolyte pump.

It will thus be observed that I have provided an improved apparatus for electroplating which eliminates the possibility of exhaustion of the supply of plating metal in the solution inside the barrel, which may occur when the barrel wall apertures are made very small.

The present barrels involve a new method of handling the electrolyte and causing the electrolyte to be changed periodically and frequently in the barrel, and causing the hydrogen to be discharged frequently from the barrel, all of which is accomplished without additional expense for equipment.

With the barrels of the prior art having very small wall apertures it has been necessary periodically to lift the cylinder out of the bath to remove the solution and replace new solution in the cylinder by putting the cylinder back in the bath. This need not be done with the present improved barrels.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. An electroplating barrel unit comprising a pair of rectangular insulating supporting plates for supporting a barrel in a solution, a pair of bus bars carried by said plates and having projecting ends adapted to rest upon supports carried by a tank, each of said insulating supporting plates having a cylindrical bearing aperture, said apertures being aligned, spacing rods secured to said plates and holding the plates parallel to each other, a unitary barrel comprising a pair of end plates parallel to each other and each end plate having an outwardly projecting trunnion located in one of said bearing apertures to rotate upon an axis at right angles to said supporting plates, each of said end plates having a groove on its inner face, and each groove being hexagonal in plan with equal sides adapted to receive the ends of a hexagonal barrel wall having one open side, said barrel wall being cemented in said grooves and having its axis eccentrically located with respect to the trunnions and bearings, each end wall being cut away on its inner surface toward the open side of said wall by an amount equal to the depth of the grooves to present a flat shoulder at each end of the open side of said barrel wall, and a cover for said open side resting on said shoulder at each end of the cover and engaging the edges of the open side of the barrel, the eccentric barrel rising and falling relative to an electroplating solution in which it is immersed as it rotates, and the barrel wall having a multiplicity of apertures, causing the solution in the barrel to be changed constantly.

2. An electroplating barrel unit according to claim 1, in which the cover is provided with edge flanges overlapping the barrel wall on each side of the opening and the cut-out portion of the end plates is widened to pass the cover and end flanges into closing position.

3. An electroplating barrel unit according to claim 1, in which the end plates of the barrel are circular and one of the end plates is cemented to a driving gear for rotating the barrel.

References Cited in the file of this patent UNITED STATES PATENTS 1,790,289 Thompson I an. 27, 1931 FOREIGN PATENTS 110,248 Great Britain Oct. 18, 1917 528,271 Italy June 11, 1955 

1. AN ELECTROPLATING BARREL UNIT COMPRISING A PAIR OF RECTANGULAR INSULATING SUPPORTING PLATES FOR SUPPORTING A BARREL IN A SOLUTION, A PAIR OF BUS BARS CARRIED BY SAID PLATES AND HAVING PROJECTING ENDS ADAPTED TO REST UPON SUPPORTS CARRIED BY A TANK, EACH OF SAID INSULATING SUPPORTING PLATES HAVING A CYLINDRICAL BEARING APERTURE, SAID APERTURES BEING ALIGNED, SPACING RODS SECURED TO SAID PLATES AND HOLDING THE PLATES PARALLEL TO EACH OTHER, A UNITARY BARREL COMPRISING A PAIR OF END PLATES PARALLEL TO EACH OTHER AND EACH END PLATE HAVING AN OUTWARDLY PROJECTING TRUNNION LOCATED IN ONE OF SAID BEARING APERTURES TO ROTATE UPON AN AXIS AT RIGHT ANGLES TO SAID SUPPORTING PLATES, EACH OF SAID END PLATES HAVING A GROOVE ON ITS INNER FACE, AND EACH GROOVE BEING HEXAGONAL IN PLAN WITH EQUAL SIDES ADAPTED TO RECEIVE THE ENDS OF A HEXAGONAL BARREL WALL HAVING ONE OPEN SIDE, SAID BARREL WALL BEING CEMENTED IN SAID GROOVES AND HAVING ITS AXIS ECCENTRICALLY LOCATED WITH RESPECT TO THE TRUNNIONS AND BEARINGS, EACH 